docs: def _headers(self):
          """Ensure the Authorization Header has a valid Access Token."""
          if not self.access_token or not self.access_token_expires:
              self._basic_login()
  
          elif datetime.now() > self.access_token_expires - timedelta(seconds=30):
              self._basic_login()
  
          return {'Accept': HEADER_ACCEPT,
                  'Authorization': 'bearer ' + self.access_token}